type color = Red | Blue | Black | White
    
val init_graphics : Vector.speed -> GDraw.drawable -> unit
  
val set_line_width : int -> unit 
val set_color : color -> unit
val draw_vector : Vector.vector -> Vector.vector -> unit
val draw_line : Vector.vector -> Vector.vector -> unit
val draw_point : Vector.vector -> unit	    
val draw_circle : Vector.vector -> Vector.speed -> unit
val draw_area : Vector.vector -> Vector.speed -> unit
